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Engineers test an idea for a new hovering rover

Caption: MIT’s aerospace engineers are testing the concept of a hovering rover that emerges using the natural charge of the Moon. This figure shows a conceptual image of a rover.Credit: Massachusetts Institute of Technology

MIT aerospace engineers are testing a new concept of hovering rover that emerges using the natural charge of the Moon.

Because they lack the atmosphere, other airless objects such as the Moon and asteroids can form electric fields when exposed directly to the Sun and surrounding plasmas. On the moon, this surface charge is strong enough to levitate dust above a meter above the ground. This is the same as static electricity causing human hair to stand upright.

Engineers at NASA and elsewhere have recently used this natural surface charge to levitate gliders with wings made of Mylar, a material that naturally retains the same charge as the surface of an airless object. Proposed. They reasoned that similarly charged surfaces should repel each other with the force that lifts the glider off the ground. However, such designs will probably be limited to small asteroids. Because larger planets are stronger and have the power to counter gravity.

The MIT team’s levitation rover may be able to work around this size limit. A concept similar to a retro disc-shaped flying saucer uses a small ion beam to charge the vehicle and increase the natural charge on the surface. The overall effect is designed to generate a relatively large repulsive force between the vehicle and the ground, requiring very little power. In the first feasibility study, researchers show that such ion boosts must be strong enough to levitate large asteroids such as small two-pound vehicles and Psyche on the Moon. I am.

“We are thinking of using this like the Hayabusa mission initiated by the Japanese space agency,” said Oliver Jia-Richards, a graduate student in MIT’s aerospace engineering department and lead author. “The spacecraft operated around a small asteroid and deployed a small rover on its surface. Similarly, future missions could send a small hovering rover to explore the surface of the moon and other asteroids. I think I can do it. “

The result of the team is Journal of spacecraft and rockets.. The co-author of Jia-Richards is M. Paulo Lozano, Professor of Aerospace Engineering at Alemán-Velasco and Director of the Space Propulsion Institute at MIT. Former visiting student Sebastian Hampl is currently enrolled at McGill University.

Ion power

The team’s levitation design relies on the use of small ion thrusters called ionic liquid ion sources. These small microfabricated nozzles are connected to a reservoir containing ionic liquids in the form of molten salt at room temperature. When a voltage is applied, the liquid ions are charged and emitted as a beam from the nozzle with a specific force.

Lozano’s team has pioneered the development of ion thrusters and has used them primarily to propel and physically maneuver small satellites in space. Recently, Rosano saw a study showing the levitation effect of the lunar charged surface on lunar dust. He also considered and wondered about NASA’s design of electrostatic gliders. Can a rover with ion thrusters generate enough repulsive and electrostatic forces to float on the moon and larger asteroids?

To test the idea, the team first modeled a small disc-shaped rover with an ion thruster that only charges the vehicle. They modeled a thruster that emits a beam of negatively charged ions from the vehicle, as well as a positively charged surface of the Moon. This effectively gave the vehicle a positive charge. However, they found that this was not enough to get the vehicle off the ground.

“Then I wondered what would happen if I transferred my charge to the surface to supplement the natural charge,” says Jia-Richards.

The team said that by directing additional thrusters to the ground and emitting cations to amplify the surface charge, the boost would generate more force on the rover and would be sufficient to lift the rover off the ground. I thought. They created a simple mathematical model of the scenario and found that it works in principle.

Based on this simple model, the team predicts that a small rover weighing about 2 pounds can achieve a levitation of about 1 centimeter above the ground on a large asteroid such as Pushke using a 10 kilovolt ion source. Did. To get a similar lift-off on the moon, you need a 50 kilovolt power supply on the same rover.

“This kind of ion design produces a lot of voltage with very little power,” Lozano explains. “The power required is so small that this can be done almost for free.”

Paused

To ensure that the model could occur in the real environment of the universe, they performed a simple scenario in Lozano’s lab. Researchers have created a small hexagonal test vehicle that weighs about 60 grams and measures the size of the palm of your hand. They installed one upward ion thruster and four downward ion thrusters, and suspended the vehicle from two springs tuned to counter the Earth’s gravity to the aluminum surface. The entire setup was placed inside a vacuum chamber to simulate the airless environment of the moon and asteroids.

Researchers also hung a tungsten rod from the experimental spring and used its displacement to measure the force generated each time the thruster was fired. They applied different voltages to the thrusters, measured the resulting force and used it to calculate the height at which the vehicle alone could levitate. They found that the results of these experiments were consistent with the predictions of the same scenario from the model, giving conviction that the predictions for hovering Rover on Pushke and the Moon were realistic.

Current models are simply designed to predict the conditions needed to achieve levitation. This happened to be about a centimeter off the ground for a two-pound vehicle. Ion thrusters can generate more force at higher voltages to lift the vehicle higher from the ground. However, Jia-Richards states that the model needs to be modified because it does not consider how the emitted ions behave at higher altitudes.

“In principle, with better modeling, we were able to levitate to a much higher height,” he says.

In that case, Rosano states that future missions to the Moon and asteroids can use ion thrusters to deploy rover to safely hover and steer unknown uneven terrain.

“With a levitating rover, you don’t have to worry about wheels or moving parts,” says Lozano. “The asteroid’s terrain can be completely non-uniform, and with a controlled mechanism to keep the rover afloat, it’s possible to create highly undulating unexplored terrain without having to physically dodge the asteroid. You can cross it. ”


Mini Rover CADRE navigates the lunar surface of SLOPE


For more information:
Oliver Jia-Richards et al, Electrostatic levitation on a low-atmospheric planet with ionic liquid ion sources, Journal of spacecraft and rockets (2021). DOI: 10.2514 / 1.A35001

Provided by Massachusetts Institute of Technology

This story has been republished in courtesy of MIT News (web.mit.edu/newsoffice/), a popular site covering news about MIT’s research, innovation and education.

Quote: Engineers test the idea of ​​a new hovering rover (December 21, 2021) taken from https: //phys.org/news/2021-12-idea-rover.html on December 22, 2021. increase

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